Vehicle doors usually have a lock mechanism, which often times is locked and unlocked by an electrically powered actuator. One common design for such power lock actuators is a linear push/pull action for electrically locking and unlocking the door locking mechanism. A typical power lock actuator includes an electrical motor, and a rotary-to-linear transmission mechanism which translates rotary motion from the motor output shaft to a linear motion for locking and unlocking the door lock mechanism. The rotary-to-linear mechanism includes a reversibly rotatable screw and carriage, or a rack and pinion, wherein the motor drives a pinion gear which linearly moves the rack or carriage, which in turn is mechanically coupled to the lock mechanism of the door.
It is customary for motor vehicle doors to be provided with locks having a manual release mechanism inside the vehicle and a key-operated mechanism accessible from outside the vehicle. If the screw/carriage or rack and pinion is directly linked to the locking mechanism, manual operation with a key may be hindered or rendered difficult since the motor has to be back driven. In order to allow back drive, it is known in the industry to provide a clutch mechanism between the electric motor and lock actuator, whereby the clutch couples the motor and actuator only when the motor is energized. When the motor is not energized, the actuator functions independently from the motor. Conventional slip clutch driven actuators for a vehicle door lock typically have a limited life due to the hard start and stop of the clutch engagement, which creates excessive wear on the screw/carriage or rack and pinion assembly. For example, see U.S. Pat. No. 6,109,124.
Accordingly, a primary objective of the present invention is the provision of an improved actuator for a vehicle door lock mechanism having enhanced actuator life.
Another objective of the present invention is the provision of a power lock actuator for a vehicle door lock which provides for soft start and stop functioning of the actuator so as to minimize wear and maximize life of the actuator.
Another objective of the present invention is the provision of a power lock actuator for a vehicle door lock mechanism which allows for actuation in both electrical and manual modes.
A further objective of the present invention is the provision of a power lock actuator for a door lock mechanism which accommodates back drive of the motor.
Still another objective of the present invention is the provision of a power lock actuator for a door lock mechanism having a centrifugal clutch with a dual-lobe drive gear to minimize start and stop loads on the linear actuator.
Yet another objective of the present invention is the provision of a power lock actuator for a door lock mechanism having a centrifugal clutch which pulses energy from the motor to the linear drive.
A further objective of the present invention is the provision of a power lock actuator for a door lock mechanism having a centrifugal clutch which produces a sine wave pulse for the linear actuator.
Another objective of the present invention is the provision of a power lock actuator for a door lock mechanism having minimal friction between the screw shaft and carriage of the actuator.
A further objective of the present invention is the provision of a power lock actuator for a door lock mechanism wherein the screw drive has thread segments only on one half of the shaft for reduced frictional engagement with the threads of the carriage.
Still another objective of the present invention is the provision of a power lock actuator which is economical to manufacture, yet durable and long lasting.
These and other objectives will become apparent from the following description of the invention.